Optical disk devices such as DVD (Digital Versatile Disc) players and BD (Blu-ray Disc™) players are provided with pickups for reading out data that is stored on optical discs such as DVDs and BDs. The pickups are driven toward the inner peripheral side or the outer peripheral side of the disc through a driving mechanism such as, for example, a spindle motor (referencing, for example, Patent Citation 1).
In optical disk devices there is the need to perform positioning control with good precision in order to stop the pickup at the desired location, in order to read the optical disc properly.
Here, in optical disk devices, typically there is variability in the driving load of the driving mechanism due to component variability, such as, for example, variability in the mass of the pickups, variability in the friction in the spindle motor, and the like. The voltage amplitude or driving frequency required to drive a driving mechanism with a small driving load are less than the voltage amplitude and driving frequency required to drive a driving mechanism with a large driving load.
As a technology related to controlling the pickup positioning to handle such component variability there is, for example, a technology, disclosed in Patent Citation 2, wherein a slide error signal is used to calculate an amount of eccentricity of the driving mechanism resulting from the component variability, and adjusting the period of application of a constant voltage pulse based on the amount of eccentricity. In the optical disc device of Patent Citation 2, the constant voltage pulse is a constant voltage pulse that is large enough to absorb the variability of friction, for example, caused by the component variability. That is, it is a voltage pulse that has the voltage amplitude and driving frequency required for driving a driving mechanism with a large driving load. Moreover, in the optical disc device of Patent Citation 2, the driving voltage is gradually decreased when stopping, so as to prevent a sudden stop.
In controlling the positioning of a pickup, there is re-zeroing control for stopping the pickup at the position wherein the disc reading is to start. In re-zeroing control, when the power supply is turned ON, the pickup is moved to a mechanically limited position at the outer peripheral side of the optical disc device (hereinafter “outermost position”). In re-zeroing control, after the pickup has been moved to the outermost position, for example, it is then moved to the innermost position. In re-zeroing control, the pickup is then moved towards the outer peripheral portion of the disc, and then the positioning is stopped at the starting position for reading the disc (hereinafter termed the “re-zeroing position”).
Here the use of the technology in Patent Citation 2 in controlling when moving the pickup to the outermost position enables the pickup to be stopped well at the outermost position. However, in the optical disc device of Patent Citation 2, a process for calculating the amount of eccentricity of the driving mechanism, based on a slide error signal, is necessary, which complicates the device structure. In this case, controlling the number of manufacturing steps and controlling manufacturing cost can be difficult.